Add the energy-profiling feature. Users can compile the proper (or their own) version of energymon libraries to capture power/energy data at runtime. The results are accessed through heartbeats.
Additionally, there are a couple of python scripts to enable heartbeats for profiler categories and process the results into some visualizations to help understand how time and energy is being spent in Servo.
Source-Repo: https://github.com/servo/servo
Source-Revision: 7b6c341900a66d1177fdc3f46705e9fb07a5b1dc